It is possible to minimalize trojita main window to systray and then main window act as hidden. If you open new composer window, then minimalize trojita to systray and then close composer window (e.g. by close button or automatically when mail sent), trojita immediately quit. Same happen if trojita is in systray and some error message dialog will show. After closing dialog, trojia quit too.
Please go ahead and submit a patch for this. It is probably related to our (broken) handling of the "quit on last window close" flag.
Git commit 61842237f0cc33922d9872097e824f011fc397b4 by Pali Rohár. Committed on 04/09/2013 at 13:27. Pushed by jkt into branch 'master'. Do not quit application on last closed window when running in systray REVIEW: 112515 M +4 -0 src/Gui/Window.cpp http://commits.kde.org/trojita/61842237f0cc33922d9872097e824f011fc397b4